We only do baths when needed and only part that needs bathing (for older pigs and for my pig that had bladder problems, that was pretty much just the hind end.) I would run a low amount of water in the sink, put a facecloth down to keep it from getting slippery, and would stand them in the sink with their bum in the water and my other hand supporting their front half and shampoo with the other hand. Sundae (my previous old girl with bladder problems) got quite a few baths like this and, although she didn't enjoy them, we got good at making it quick and keeping her minimally wet. The hardest part was getting her dry afterwards, she was scared of dryer noise and hated having her back end rubbed down with a towel! We just would sit her on a towel, give her treats to distract her, and basically try to blot her dry over time!